In forming wiring included in a semiconductor device, a barrier metal film such as a TiN film and a Ti film is formed. Examples of a method of forming the TiN film are a sputtering method, a MOCVD (Metal Organic Chemical Vapor Deposition) method, and the like. The MOCVD method has an advantage of high coverage.
In forming the TiN film by the MOCVD method, tetrakis (dimethylamino)titanium (TDMAT: Ti[N(CH3)2]4) is mainly used a raw material. TDMAT is especially effective when used after the formation of Al wiring because it is thermally decomposed at relatively low temperatures.
However, since TDMAT contains carbon, carbon and hydrocarbon are easily taken into the TiN film. The TiN film, when carbon or hydrocarbon is taken thereto, increases in specific resistance and thus cannot exhibit a desired characteristic.
Therefore, the conventional method has a process of removing carbon and hydrocarbon by irradiating a TiN film with plasma after forming the TiN film with a thickness of about 10 nm or less. A reason why the thickness of the TiN film is set to about 10 nm or less is that even the plasma irradiation cannot completely remove carbon and so on if the TiN film has a larger thickness than this. Incidentally, RF power for the plasma irradiation is about 750 W.
In this method, however, the number of processes increases as the thickness that the TiN film is required to have is larger. For example, when a TiN film with 20 nm is necessary, it is necessary to repeat the formation of the TiN film at least twice and the plasma irradiation at least twice. As an extreme example, when a TiN film with 100 nm is necessary, it is necessary to repeat the formation of the TiN film at least ten times and the plasma irradiation at least ten times. Therefore, it cannot be said that a throughput is sufficiently high. Further, as the number of times of the plasma irradiation increases, semiconductor elements such as transistors already formed are more damaged.
Increasing the RF power of the plasma irradiation enables a high throughput, but accordingly gives a greater damage to the semiconductor elements. Conversely, decreasing the RF power enables a reduction in the damage to the semiconductor elements, but accordingly lowers the throughput.
Patent document 1: Japanese Laid-open Patent Publication No. 2006-161163
Patent document 2: Japanese Laid-open Patent Publication No. 2001-326192
Patent document 3: Japanese Laid-open Patent Publication No. 2000-286215